Constructed Fluid Systems 9.2

9.2 Key Terms and Objectives Hydraulics Hydraulic Systems Hydraulic Multiplication Pneumatics Pneumatic Systems

Objectives Can explain how pressure in fluids at rest and fluids in motion can produce a force to operate mechanical devices How hydraulic systems create pressure that moves through a liquid such as oil or water How hydraulic systems can greatly multiply force. Explain how in pneumatic systems, an enclosed gas such as air transmits a force causing motion.

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Fluids At Rest Blaise Pascal studied fluid systems and observed when you apply a pressure to a certain point in an enclosed system, that pressure is transmitted equally through an entire system. Think of a tube of toothpaste or squeezing a balloon This squeezing creates static pressure

Static Pressure Static pressure is pressure exerted by a liquid or gas that is not in motion This static pressure now capable of applying a force, even though it is not moving eg. Pressing brakes

Fluids at Rest and in Motion Fluids in motion Bernoulli discovered the concept of dynamic pressure Fluids in motion cause a decrease in pressure perpendicular to the direction of motion Dynamic pressure is created when fluid moves Air moving faster over the wing creates higher pressure underneath = lift force

Hydraulic Systems Hydraulics = study of pressure in liquids Hydraulic systems create pressures that travel through a fluid Pressure applied to an enclosed fluid creates a force that can be used anywhere A pump is generally used to provide pressure at one point Everywhere in the system then has a usable force This is why we have pressure in our taps and faucets Pumps may create high or low pressure to move fluids

Valves and Hydraulic Multiplication Valves are used to control the movement of fluids Therefore, valves control the location of fluid pressure Check valves only allow fluids to flow in one direction Hydraulic multiplication allows small changes in pressure to do large amounts of work. A small area applying pressure can cause a large force to be exerted over a large area.

Problems in Hydraulic Systems Hydraulic systems must be designed carefully Minimize twists and turns to allow fluid to flow freely Connect pipes and seams well to avoid leakage Pressure in the system is affected by the size of the pipes and the smoothness of the inside of the pipes. Pressures can be dangerous if fluids allowed to escape through broken pipes or lines. Pressure-relief valves re often used to control pressures Fluids are often poisonous

Pneumatic Systems Pneumatic systems use a gas under pressure Same idea as hydraulics, except gases can be compressed, whereas fluids do not compress much. Compressors are used in pneumatic systems, not pumps Compressors build up pressure, then quickly release it in a small area to produce large forces Pneumatics can be used in large and small systems Pneumatics and hydraulics are often used together

Pneumatic Systems and their Problems Pneumatic systems must have unblocked air flow to work efficiently. Because air is usually brought into a compressor to increase pressure, filters clean the air to keep the compressor clean If the filters are not cleaned, the pneumatic system becomes inefficient What did we do before email attachments and faxes? This Rohrpost station used pneumatics to “shoot” tubes with rolled up documents around large building like factories. If the station’s compressor filter was blocked, important messages could become lost. Video